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'\" Copyright (c) 1996 Sun Microsystems, Inc.

'\"

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'\" RCS: @(#) $Id: MeasureChar.3,v 1.1.1.1 2002-01-16 10:25:48 markom Exp $

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.so man.macros

.TH Tk_MeasureChars 3 "" Tk "Tk Library Procedures"

.BS

.SH NAME

Tk_MeasureChars, Tk_TextWidth, Tk_DrawChars, Tk_UnderlineChars \- routines to measure and display simple single-line strings.

.SH SYNOPSIS

.nf

\fB#include \fR

.sp

int

\fBTk_MeasureChars(\fItkfont, string, maxChars, maxPixels, flags, lengthPtr\fB)\fR

.sp

int

\fBTk_TextWidth(\fItkfont, string, numChars\fB)\fR

.sp

void

\fBTk_DrawChars(\fIdisplay, drawable, gc, tkfont, string, numChars, x, y\fB)\fR

.sp

void

\fBTk_UnderlineChars(\fIdisplay, drawable, gc, tkfont, string, x, y, firstChar, lastChar\fB)\fR

.sp

.SH ARGUMENTS

.AS "const char" firstChar

.AP Tk_Font tkfont in

Token for font in which text is to be drawn or measured.  Must have been

returned by a previous call to \fBTk_GetFont\fR.

.AP "const char" *string in

Text to be measured or displayed.  Need not be null terminated.  Any

non-printing meta-characters in the string (such as tabs, newlines, and

other control characters) will be measured or displayed in a

platform-dependent manner.

.AP int maxChars in

The maximum number of characters to consider when measuring \fIstring\fR.

Must be greater than or equal to 0.

.AP int maxPixels in

If \fImaxPixels\fR is greater than 0, it specifies the longest permissible

line length in pixels.  Characters from \fIstring\fR are processed only

until this many pixels have been covered.  If \fImaxPixels\fR is <= 0, then

the line length is unbounded and the \fIflags\fR argument is ignored.

.AP int flags in

Various flag bits OR-ed together: TK_PARTIAL_OK means include a character

as long as any part of it fits in the length given by \fImaxPixels\fR;

otherwise, a character must fit completely to be considered.

TK_WHOLE_WORDS means stop on a word boundary, if possible.  If

TK_AT_LEAST_ONE is set, it means return at least one character even if no

characters could fit in the length given by \fImaxPixels\fR.  If

TK_AT_LEAST_ONE is set and TK_WHOLE_WORDS is also set, it means that if

not even one word fits on the line, return the first few letters of the

word that did fit; if not even one letter of the word fit, then the first

letter will still be returned.

.AP int *lengthPtr out

Filled with the number of pixels occupied by the number of characters

returned as the result of \fBTk_MeasureChars\fR.

.AP int numChars in

The total number of characters to measure or draw from \fIstring\fR.  Must

be greater than or equal to 0.

.AP Display *display in

Display on which to draw.

.AP Drawable drawable in

Window or pixmap in which to draw.

.AP GC gc in

Graphics context for drawing characters.  The font selected into this GC

must be the same as the \fItkfont\fR.

.AP int "x, y" in

Coordinates at which to place the left edge of the baseline when displaying

\fIstring\fR.

.AP int firstChar in

The index of the first character to underline in the \fIstring\fR.

Underlining begins at the left edge of this character.

.AP int lastChar in

The index of the last character up to which the underline will

be drawn.  The character specified by \fIlastChar\fR will not itself be

underlined.

.BE

.SH DESCRIPTION

.PP

These routines are for measuring and displaying simple single-font,

single-line, strings.  To measure and display single-font, multi-line,

justified text, refer to the documentation for \fBTk_ComputeTextLayout\fR.

There is no programming interface in the core of Tk that supports

multi-font, multi-line text; support for that behavior must be built on

top of simpler layers.

.PP

A glyph is the displayable picture of a letter, number, or some other

symbol.  Not all character codes in a given font have a glyph.

Characters such as tabs, newlines/returns, and control characters that

have no glyph are measured and displayed by these procedures in a

platform-dependent manner; under X, they are replaced with backslashed

escape sequences, while under Windows and Macintosh hollow or solid boxes

may be substituted.  Refer to the documentation for

\fBTk_ComputeTextLayout\fR for a programming interface that supports the

platform-independent expansion of tab characters into columns and

newlines/returns into multi-line text.

.PP

\fBTk_MeasureChars\fR is used both to compute the length of a given

string and to compute how many characters from a string fit in a given

amount of space.  The return value is the number of characters from

\fIstring\fR that fit in the space specified by \fImaxPixels\fR subject to

the conditions described by \fIflags\fR.  If all characters fit, the return

value will be \fImaxChars\fR.  \fI*lengthPtr\fR is filled with the computed

width, in pixels, of the portion of the string that was measured.  For

example, if the return value is 5, then \fI*lengthPtr\fR is filled with the

distance between the left edge of \fIstring\fR[0] and the right edge of

\fIstring\fR[4].

.PP

\fBTk_TextWidth\fR is a wrapper function that provides a simpler interface

to the \fBTk_MeasureChars\fR function.  The return value is how much

space in pixels the given \fIstring\fR needs.

.PP

\fBTk_DrawChars\fR draws the \fIstring\fR at the given location in the

given \fIdrawable\fR.

.PP

\fBTk_UnderlineChars\fR underlines the given range of characters in the

given \fIstring\fR.  It doesn't draw the characters (which are assumed to

have been displayed previously by \fBTk_DrawChars\fR); it just draws the

underline.  This procedure is used to underline a few characters without

having to construct an underlined font.  To produce natively underlined

text, the appropriate underlined font should be constructed and used.

.SH KEYWORDS

font